support for Awaitable objects in `asyncio.wait` removed in 3.11

[graingert]

on python3.10 -W error this passes:

class ExampleAwaitable:
    def __await__(self):
        async def _():
            return await asyncio.sleep(0)

        return _().__await__()


import asyncio

print(f"{asyncio.iscoroutine(ExampleAwaitable())=}")

async def amain():
    await asyncio.wait([ExampleAwaitable()])
    print("waited!")

asyncio.run(amain())

and in 3.11 this fails:

asyncio.iscoroutine(ExampleAwaitable())=False
Traceback (most recent call last):
  File "/home/graingert/projects/foo.py", line 17, in <module>
    asyncio.run(amain())
  File "/usr/lib/python3.11/asyncio/runners.py", line 187, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/asyncio/runners.py", line 120, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/asyncio/base_events.py", line 650, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/home/graingert/projects/foo.py", line 14, in amain
    await asyncio.wait([ExampleAwaitable()])
  File "/usr/lib/python3.11/asyncio/tasks.py", line 427, in wait
    return await _wait(fs, timeout, return_when, loop)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/asyncio/tasks.py", line 531, in _wait
    f.add_done_callback(_on_completion)
    ^^^^^^^^^^^^^^^^^^^
AttributeError: 'ExampleAwaitable' object has no attribute 'add_done_callback'

this broke distributed and we missed the DeprecationWarning because ensure_future accepts a wider variety of objects than just futures tasks and coroutines

dask/distributed#6785

the removal happened here 903f0a0

[graingert]

I think using something like this might help?

def _insist_future(f, loop):
    f2 = ensure_future(f, loop=loop)
    if f2 is not f:
        warnings.warn("passing non-futures is deprecated")
    return f2

    fs = set(fs)
    loop = events.get_running_loop()
    if any(coroutines.iscoroutine(f) for f in fs):
        raise TypeError("Passing coroutines is forbidden, use tasks explicitly.")
    fs = {_insist_future(f, loop=loop) for f in fs}
    return await _wait(fs, timeout, return_when, loop)

[graingert]

This was intended to be deprecated in 3.10 so I'm tentatively adding the 3.10 label

[gvanrossum]

So what is the bug exactly? Was the deprecation schedule not followed properly? Or do you just disagree with the deprecation and subsequent removal? In that case, tough luck. The release manager isn't going to allow the removal to be reversed.

[graingert]

So what is the bug exactly? Was the deprecation schedule not followed properly? Or do you just disagree with the deprecation and subsequent removal? In that case, tough luck. The release manager isn't going to allow the removal to be reversed.

The deprecation schedule was not followed properly. The removal didn't match the deprecation, and support for iterables was removed. There's more discussion on the PR

[gvanrossum]

Now that the PR is closed, can you come up with a better description? It should describe a desired course of action.